In the context of the present disclosure a portable electronic device should be understood as a small microelectronic device designed to be worn on the human body. Especially the portable electronic devices may be adapted to be at least partly worn at or in the human ear. Examples of such devices include hearing aids and some types of portable electronic sensor systems.
A variety of hearing aid types exist and a few of these are further described below. Behind-The-Ear (BTE) hearing aids are worn behind the ear. To be more precise an electronics unit comprising a housing containing the major electronics parts thereof is worn behind the ear. An earpiece for emitting sound to the hearing aid user is worn in the ear, e.g. in the concha or the ear canal. A connector connects the earpiece to the housing. In a traditional BTE hearing aid, a sound tube is used because the output transducer, which in hearing aid terminology is normally referred to as the receiver, is located in the housing of the electronics unit. In some modern types of hearing aids a conducting member comprising electrical conductors is used, because the receiver is placed in the earpiece in the ear. Such hearing aids are commonly referred to as Receiver-In-The-Ear (RITE) hearing aids. In a specific type of RITE hearing aids the receiver is placed inside the ear canal. This is known as Receiver-In-Canal (RIC) hearing aids.
In-The-Ear (ITE) hearing aids are designed for arrangement in the ear, normally in the funnel-shaped outer part of the ear canal. In a specific type of ITE hearing aids the hearing aid is placed substantially inside the ear canal. This type is known as Completely-In-Canal (CIC) hearing aids. This type of hearing aid requires a very compact design in order to allow it to be arranged in the ear canal, while accommodating the components necessary for operation of the hearing aid. Other types of hearing aids include cochlear implants and bone conducting hearing aids. Other devices that resemble hearing aids are e.g. devices for the treatment of tinnitus and devices for relieving stress and anxiety.
A great variety of portable electronic sensor systems exist that qualify as portable electronic devices in the context of the present disclosure. One variety is systems comprising means for EEG monitoring. These systems are applicable for a lot of medical purposes such as:                monitoring the user's brain waves for evaluation of the result of a medical treatment;        monitoring the user's brain waves for detection of medical states, and possibly alerting the user, caretakers, or relatives, wherein examples of such medical states are impending hypoglycemia and epileptic seizures;        monitoring the user's brain waves for the purpose of diagnosing medical conditions. Examples of such conditions are epileptic conditions such as absence epilepsy, neurodegenerative conditions such as Parkinson's disease, and psychiatric disorders such as Schizophrenia or Anxiety disorders;        providing Audio Feedback for the purpose of treating a disease or a disorder such as Attention Deficit Hyperactivity Disorder (ADHD), tinnitus, or phantom pain sensations; and        providing a Brain-Computer Interface or Man-Machine Interface for enabling the user to control the device it-self or for controlling peripheral devices.        
A range of standard batteries such as e.g. batteries of the Zn-air type are suitable for powering a portable electronic device according to the invention.
However, e.g. Zn-air batteries are disadvantageous in that they are not very environmentally friendly because they are not re-chargeable and contain mercury. Consequently a drive towards more environmental friendly power sources exists.
Within the art of hearing aids it has therefore been proposed to use fuel cells as power source.
DE-A1-10115429 discloses a hearing aid powered by a fuel cell capable of providing a voltage of 1.19 V.
Fuel cells are an environmentally friendly power source, but generally fuel cells are not capable of meeting the power requirements while at the same time fulfilling the strict size limitations that are required in present portable electronic devices. If fuel cells are stacked the output voltage can be increased but this generally comes at the cost of an increase in both complexity and size of the fuel cell and thereby the portable electronic device comprising the fuel cell. Alternatively the fuel cell can be implemented in a configuration where the fuel cell charges a second battery (e.g. of the Li-ion type), whereby the output voltage can be controlled by the second battery and the load dependence mitigated, but this solution also comes at the cost of an increase in size of the portable electronic device comprising the fuel cell configuration.
It is therefore a feature of the present invention to provide a portable electronic device that can be powered by a low voltage fuel cell.
It is another feature of the present invention to provide a portable electronic device that is powered by a low voltage fuel cell and optimized with respect to miniaturization of the device.
It is yet another feature of the present invention to provide a portable electronic device that is powered by a low voltage fuel cell and optimized with respect to mitigation of the load dependence of the fuel cell.